When the epiphyseal plate becomes a line, what happens to the epiphyseal plate?

• A. Thins
• B. Thickens
• C. Disappears
• D. Stops growing

Answer: (A)

Growth plates grow through endochondral ossification, where cartilage is gradually replaced by bone. When the plate is transitioning to a line, the cartilage is being laid down less and bone formation continues, so the remaining growth zone narrows. This thinning reflects the plate approaching right before full ossification into the epiphyseal line. Once it has become a line, longitudinal growth has essentially stopped, but the immediate change described by becoming a line is that the plate has thinned and is nearing full conversion to bone. So the best description is that the epiphyseal plate thins.